Circuit breaker enclosure

ABSTRACT

An enclosure, for a circuit breaker, is provided with a venting arrangement to allow release of internal pressure caused by a short circuit fault condition in the circuit breaker. The venting arrangement is provided in the form of a blow out panel mounted over an aperture formed in the enclosure. Insulating barriers are provided to prevent vented exhaust particles from coming into contact with electrically live conductors.

The invention relates to circuit breakers and more particularly tomoulded case circuit breakers (M.C.C.B), enclosures therefor and to anI-line panelboard for mounting such circuit breaker enclosures.

With M.C.C.B.'s fitted with enclosures problems can occur when suchbreakers open under short circuit conditions since gas and particles aregenerated under such conditions. This can cause problems with damage tothe M.C.C.B. enclosure by pressure build up and furthermore thegenerated particles can impair the dielectric withstand of theelectrical circuits throughout the panelboard assembly.

It is an object of the present invention to obviate or mitigate theseabove disadvantages.

According to one aspect of the invention there is provided an enclosure,for a circuit breaker, formed with at least one venting arrangement toallow release of internal pressure caused by short circuit faultconditions, in use.

A venting arrangement may be provided in the form of a glow out panel ora flap mounted over an aperture formed in the enclosure and the panel orflap may be formed of synthetic plastics material.

In addition or alternatively a venting arrangement may comprise louvresformed in the enclosure.

Insulating barriers may be located to prevent vented exhaust particlesform coming into contact with electrically live conductors, in use.

According to a further aspect of the invention there is provided anI-line panelboard for locating a plurality of circuit breaker assembliestherein, the panelboard being formed to provide a central verticalexpansion chamber located between two vertical stacks of juxtaposedplug-in circuit breaker assemblies.

A panel of synthetic plastics material may be located at the lower endof the expansion chamber for protecting a bus stack located therebelow.

A fixed or sprung loaded centre cover may be located over the verticalexpansion chamber.

The panelboard may have a plurality of circuit breaker enclosures, asdefined in the fourth to seventh paragraphs hereinbefore, locatedtherein.

The foregoing and further features of the invention may be more readilyunderstood from the following description of preferred embodimentsthereof, by way of example, with reference to the accompanying drawings,in which:

FIG. 1 is a perspective view of the front of an I-line panelboard;

FIG. 2 is a side elevational view of a portion of the panelboard of FIG.1 showing a centre cover located thereon;

FIGS. 3a and 3b are view, on enlarged scale, of the circled portion A ofFIG. 2 showing alternative fixings for the centre cover;

FIG. 4 is a side elevational view of an M.C.C.B. enclosure plug-in unitinserted into the stack of the panelboard;

FIG. 5 is an end elevational view of the end of the unit of FIG. 4remote from the stack;

FIG. 6 is an end elevational view of the other end of the unit of FIG. 4adjacent to the stack;

FIG. 7 is an end elevational view of an alternative arrangement to FIG.6;

FIG. 8 is a side elevational view of an alternative M.C.C.B. enclosureplug-in unit, and

FIG. 9 is an end elevational view in the direction of arrow B on FIG. 8.

Referring now firstly to FIG. 1 there is shown an I-line panelboardassembly 10 with two vertical stacks of plug-in enclosed M.C.C.B.'s 11shown located in their plugged-in positions. Each of the M.C.C.B.'senclosures 11 is vented into a central vertical expansion chamber 12 ana cover 13 of synthetic plastics material is located at the lower endfor protecting a bus stack (not shown) located therebelow. TheM.C.C.B.'s enclosures 11 may be vented in a plurality of forms withenclosure 11a being formed with a vent opening 14, enclosure 11b havinga panel 15 which is secured at its edges to form a "blow-out" panel andenclosure 11c having a flap 16 which is rigidly secured at one edge andwhich may be perforated, both the panel 15 and the flap 16 being formedof synthetic plastics material. The detail of such venting will bedescribed in more detail hereinafter. Customer cabling compartments arelocated vertically at each side of the assembly 10 beneath panels 17. Acentral cover 18 (FIG. 2) is located over the expansion chamber 12 inthe position indicated by arrow 18a.

Referring now to FIG. 2 there is shown the panelboard bus stack 19, thecentral cover 18 which is located over the expansion chamber 12 and astack barrier 20 located between stack 19 and cover 18. FIG. 3a shows,on enlarged scale, the circled portion A in FIG. 2 and shows the detailof an assembly 21 comprising a nut and bolt fixing with a pre-loadedspring to enable release movement of cover 18 should there be excessivepressure build-up within chamber 12. FIG. 3b shows a similar view toFIG. 3a but with a fixed nut and bolt assembly 22.

Referring now to FIGS. 4 and 5 there is shown an enclosure 11 which isplugged-in to stack 19. With this enclosure 11 the outer end face isformed with venting louvres 23 which may be provided as an alternativeor additional to an aperture 14, panel 15 or flap 16 at the stackengaging end. Cable entry into the enclosure 11 is via holes 24 whichare drilled to suit the cable size to be utilized.

Referring now to FIG. 6 there is shown an end elevational view of theenclosure 11c of FIG. 1 on enlarged scale. The flap 16 is rigidlylocated along the base by screws 25 and a slotted perforation 26provided to enable hingeing or snap-off with pressure build up withinenclosure 11c. FIG. 7 shows a similar view to FIG. 6 for the enclosure11b, in which panel 15 is located by the edges of screw mounted washers27 so as to provided a "blow-out" panel with pressure build up withinenclosure 11b.

Referring now to FIGS. 8 and 9 there is shown a further enclosure 11with details of protection of the electrical connections 28 fromcontamination from generated particles when the breaker opens undershort circuit conditions. An indicating barrier 29 is provided at theouter edges of the connections and further barriers 30 are providedbetween the connections. Furthermore barriers 31 are located over andaround the terminal pads 32 of the breaker.

Hence it will be seen that when breakers open under short circuitconditions the arrangements shown provide venting of gaspressure/particles to both prevent mechanical damage which could resultin the environmental degree of protection being impaired and thatparticles released to not contaminate the electrical connections.

We claim:
 1. An enclosure, for enclosing a circuit breaker thereinthereby segregating the circuit breaker from other circuit breakers,said enclosure is formed with a venting arrangement to allow release ofinternal pressure caused by short circuit fault conditions, wherein saidventing arrangement includes an aperture, disposed in said enclosure;and a blow out panel secured at its edges over the entire aperture tothereby cover the aperture, but adapted to be blown open under highpressure conditions, to uncover said aperture, thereby releasing thepressure out of said enclosure.
 2. An enclosure as claimed in claim 1wherein the panel is formed of synthetic plastics material.
 3. Anenclosure as claimed in any preceding claim including insulatingbarriers adapted to prevent vented exhaust particles from coming intocontact with electrical connections, wherein said insulating barriersare located around the connections.
 4. An enclosure assembly forenclosing a circuit breaker therein, said enclosure assemblycomprising:an enclosure for enclosing the circuit breaker thereinthereby segregating the circuit breaker from other circuit breakers,said enclosure including electrical connections for coupling wireconductors to the circuit breaker; a venting arrangement, disposed insaid enclosure, for releasing internal pressure caused when the circuitbreaker interrupts under a short circuit fault condition, saidarrangement including an aperture formed in said enclosure; and ablow-out panel secured at its edges over the entire aperture to therebycover the aperture, but adapted to be blown open under high pressureconditions, to uncover said aperture, thereby releasing the highpressure out of said enclosure; and a set of barriers adapted forsurrounding the electrical connections, said barriers preventcontamination to the electrical connections from particles generatedwhen the circuit breaker interrupts due to the short circuit condition.